I enjoyed it, you can go for a half or fullday. the staff were very friendly and the full day price include lunch, which was excellent, I think you can pay for lunch if you only do the half day. endless supply of hot & cold drinks. The vehicle they had on the day I went were, L/rover, Bedford mk, 432 and an Abbott.
we were divided into groups and took turns, there was three to a group when i visited. I dont what the age restriction is for driving but there is a viewing area.
If you want to have a bit of fun then it is worth travelling, conkers is nearby.